Superman and Thanos
Superman didn’t need to wear an Infinity Gauntlet to show he could move planets as Thanos did in Marvel’s Avengers: Infinity War. Moving planets is no problem for Superman. Can Superman beat Thanos with the Infinity Gauntlet? Let’s put it clear: no matter how strong, durable or fast you are, the one who wields the Gauntlet is infinite times more strong, durable and fast than you. So, yeah, Superman defeating Thanos with IG can only be seen on fanfiction of a die-hard Superman fan. Unless Thanos threw the fight, Superman could never win.
Superman’s Victories
Despite all evidence to the contrary, Superman soundly defeated Thor when the two heroes actually fought. But when Thor tried to knock Superman out with his hammer, Superman knocked Thor out with one final punch.
Superman vs. Hulk
Years of reading DC comic books. No Superman can’t beat Thanos, Thanos has him outclassed in every aspect except speed, which is useless for Superman. Hulk vs MCU Hulk The polished fighting style of Thanos proved too much for Hulk and his overall brutality and savagery. Hulk had the upper hand for all of two seconds due to the element of surprise before Thanos was able to finish the fight with a few quick blows. This bout has a clear winner: Thanos.
Superman and the Avengers
If a fight broke out between Superman and the Avengers, the Avengers would defeat Superman. They could easily overwhelm Superman from all directions. Moreover, Ant-Man, Doctor Strange, and Thor, who possess magical powers could tactically defeat Superman.
Other Powerful Characters
Dormammu
One established MCU villain who is more powerful than Thanos is Doctor Strange’s Dormammu, who could easily return as an antagonist in Doctor Strange in the Multiverse of Madness. In his own world, the Lord of the Dark Dimension is nearly unbeatable.
The Strongest Superhero
The Hulk Bruce Banner found himself transformed into a monster known only as "Hulk." The details of the pair’s symbiotic relationship might change, but at the end of the day, superhero comic books have one unbreakable rule: Hulk is the strongest one there is, and that’s really all there is to it.